The present invention relates to a brush-holder plate, in particular for an electric motor of the type comprising a first portion supporting brush holders and retractable means for locking the brushes in a radially retracted position in the brush holders for the mounting of the latter on the commutator of the motor.
At the present time, all electric motors, and in particular DC motors, intended to be mounted on motor vehicles are, or will be, mounted automatically in production lines.
In this field, conventional practice has established a rule which amounts to assembling or stacking everything along a single direction parallel to the axis of rotation of the armature of the motor. However, the brushes which are adapted to supply the electric current to the commutator of the armature of the motor, are moved in a radial plane perpendicular to the rotation axis of the armature. It is recalled that the brushes, each of which is disposed in a tubular sheath which is also usually termed a "brush holder", are subjected to a force which is therefore perpendicular to the axis of the armature and is exerted by elastic means, such as springs, in the radially inwardly direction toward the commutator for ensuring a pressure of contact compatible with a good passage of the current and therefore with a minimum resistance between the brushes and the rotating commutator.
While it is relatively easy to mount the brushes and the springs in the brush holders in an automatic manner, it is practically impossible, or at least too delicate and costly in equipment, to design a system which spreads apart the brushes (i.e, pushes the brushes against the spring-bias and into a retracted position within the holders) when the commutator of the motor is introduced between the brushes during insertion of the commutator.
A certain number of brush-holder plates exist in the art which are equipped with means for locking the brushes in the retracted position when mounting the plate on the commutator. These locking means are for example formed by washers or portions of a tube pushed by the commutator upon assembly. However, these devices have a number of drawbacks in that they are relatively expensive and mostly cannot be recovered.